The two young Colorado girls who, along with their mother, were killed this past week may have been strangled before their bodies were dumped in an oil well, according to a court document.

A motion filed Friday by attorneys defending Christopher Watts, who investigators believe killed his pregnant wife and daughters, asks that DNA samples be taken from the children’s necks. The document cites an expert who argued that DNA would still be present on the bodies — even though they had been submerged in crude oil for four days before they were found — but that evidence would be lost once the autopsies were performed.

A Weld County judge, however, denied the request, the Denver Post reported. And authorities said Friday that they had finished the autopsies on the victims, though they did not say how they died.

The document offers the first glimpse into what may have happened to Shanann Watts, 34, and her two daughters when they disappeared Monday. The following day, Christopher Watts stood in front of a parade of news cameras and told reporters that his children were his life. His family had just vanished, he told Denver 7 ABC. “I’m living in a nightmare, and I can’t get out of it,” he told NBC affiliate KUSA.

But the media interviews were over on Wednesday, when police vehicles showed up at the Watts house. Reporters photographed officers removing bags of evidence and towing away a pickup. The Frederick Police Department arrested Christopher Watts, 33, that night on suspicion of first-degree murder and evidence tampering — three counts each.

By Thursday, authorities said that they had found the bodies of 4-year-old Belle, 3-year-old Celeste and their mother, all “in close proximity” to each other.

Christopher Watts’s attorneys sought to preserve DNA evidence they said would still be present on the bodies, saying that once autopsies are finished, the evidence will be “lost forever,” according to the motion.

The attorneys said they consulted with DNA expert Richard Eikelenboom who said in court records that he has experience taking samples from dead bodies and “getting good results after strangulation.”

“This DNA can be retrieved with a double swab technique. DNA scientists are familiar with this technique and an experienced person should take this samples. In my opinion, the presence of oil will not destroy the DNA,” Eikelenboom said.

Eikelenboom added that the hands of the children, as well as the hands and nails of their mother should all be sampled as well. He and defense attorneys did not seek swabs from the mother’s neck.

Christopher Watts is escorted into the courtroom before his bond hearing at the Weld County Courthouse on Thursday in Greeley, Colo. (Joshua Polson/Greeley Tribune/Pool/AP)

Eikelenboom is a forensic scientist who specializes in DNA trace recovery and has examined “hundreds of crime scenes,” according to Independent Forensic Services, a company he owns with his wife.

In 2016, a Denver district court judge rejected Eikelenboom as a DNA expert after he admitted to a prosecutor that he had no direct DNA extraction or analysis experience, that he operated an unaccredited lab, that he failed basic proficiency tests in 2011 and 2012, and that he was “self-trained” in running DNA profiles, the Denver district attorney’s office said. The agency also said that Eikelenboom “has committed fundamental DNA analysis errors by not following accepted scientific standards in the DNA field.”

Eikelenboom, who is from the Netherlands, said the district attorney’s office misrepresented his experience. He didn’t have experience with DNA extraction and analysis back in the 1990s, before advancements in DNA technology, he said, “but that doesn’t mean I didn’t do it in 2005 or in 2016, or that I’m not fully accredited.”

How the DNA evidence would have fit into Christopher Watts’s defense is unknown. Eikelenboom said he could not comment on the pending case. James Mason, a deputy state public defender in rural Weld County, Colo., did not respond to an email seeking comment Saturday.

Investigators have said little else about the deaths. The district attorney has until Monday to bring formal charges, at which point the arrest affidavit may be unsealed, revealing how Watts became a suspect.

The family’s life seemed idyllic. They lived in a big two-story house and Shanann Watts was pregnant with the couple’s third child. Just two months ago, she sent her husband a picture of her first ultrasound.

“Little peanut!” Christopher Watts replied.

A photograph sits amid the tributes as they grow outside the home where Shanann Watts and her daughters, Bella and Celeste, lived in Frederick, Colo. (David Zalubowski/AP)

“I love Chris! He’s the best dad us girls could ask for,” Shanann Watts wrote in a Facebook post sharing the text exchange with her husband.

Their life, apparently, wasn’t perfect. In 2015, two years after buying their house, the Wattses filed for bankruptcy. They were drowning in a $400,000 mortgage and more than $50,000 in credit card debt, bankruptcy court documents show. His paycheck as an operator for Anadarko Petroleum and hers from a children’s hospital weren’t nearly enough.

But they moved on with their lives. They struck a deal with their creditors, and Shanann Watts got a new job doing direct sales for a “lifestyle system” called Thrive. They stayed in their big two-story house, and the family kept growing.

In a statement to CBS4, Shanann Watts’s family said her husband confessed to the killings.

“It is with deep hurt, confusion and anger to confirm our beautiful cousin Shanann Watts, her unborn child, and her two angelic daughters, Bella (4), Celeste (3) were viciously murdered by husband Chris Watts,” the family said.